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authorVlastimil Babka <vbabka@suse.cz>2014-10-09 15:27:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-09 22:25:53 -0400
commit53853e2d2bfb748a8b5aa2fd1de15699266865e0 (patch)
treedd09605e9cd9a4329afc274faffae1c15e81f150 /mm/compaction.c
parent8b1645685acf3c7e0b93611fb4b328ef45c47e92 (diff)
downloadop-kernel-dev-53853e2d2bfb748a8b5aa2fd1de15699266865e0.zip
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mm, compaction: defer each zone individually instead of preferred zone
When direct sync compaction is often unsuccessful, it may become deferred for some time to avoid further useless attempts, both sync and async. Successful high-order allocations un-defer compaction, while further unsuccessful compaction attempts prolong the compaction deferred period. Currently the checking and setting deferred status is performed only on the preferred zone of the allocation that invoked direct compaction. But compaction itself is attempted on all eligible zones in the zonelist, so the behavior is suboptimal and may lead both to scenarios where 1) compaction is attempted uselessly, or 2) where it's not attempted despite good chances of succeeding, as shown on the examples below: 1) A direct compaction with Normal preferred zone failed and set deferred compaction for the Normal zone. Another unrelated direct compaction with DMA32 as preferred zone will attempt to compact DMA32 zone even though the first compaction attempt also included DMA32 zone. In another scenario, compaction with Normal preferred zone failed to compact Normal zone, but succeeded in the DMA32 zone, so it will not defer compaction. In the next attempt, it will try Normal zone which will fail again, instead of skipping Normal zone and trying DMA32 directly. 2) Kswapd will balance DMA32 zone and reset defer status based on watermarks looking good. A direct compaction with preferred Normal zone will skip compaction of all zones including DMA32 because Normal was still deferred. The allocation might have succeeded in DMA32, but won't. This patch makes compaction deferring work on individual zone basis instead of preferred zone. For each zone, it checks compaction_deferred() to decide if the zone should be skipped. If watermarks fail after compacting the zone, defer_compaction() is called. The zone where watermarks passed can still be deferred when the allocation attempt is unsuccessful. When allocation is successful, compaction_defer_reset() is called for the zone containing the allocated page. This approach should approximate calling defer_compaction() only on zones where compaction was attempted and did not yield allocated page. There might be corner cases but that is inevitable as long as the decision to stop compacting dues not guarantee that a page will be allocated. Due to a new COMPACT_DEFERRED return value, some functions relying implicitly on COMPACT_SKIPPED = 0 had to be updated, with comments made more accurate. The did_some_progress output parameter of __alloc_pages_direct_compact() is removed completely, as the caller actually does not use it after compaction sets it - it is only considered when direct reclaim sets it. During testing on a two-node machine with a single very small Normal zone on node 1, this patch has improved success rates in stress-highalloc mmtests benchmark. The success here were previously made worse by commit 3a025760fc15 ("mm: page_alloc: spill to remote nodes before waking kswapd") as kswapd was no longer resetting often enough the deferred compaction for the Normal zone, and DMA32 zones on both nodes were thus not considered for compaction. On different machine, success rates were improved with __GFP_NO_KSWAPD allocations. [akpm@linux-foundation.org: fix CONFIG_COMPACTION=n build] Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
-rw-r--r--mm/compaction.c32
1 files changed, 25 insertions, 7 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 21bf292b..1c7195d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1125,27 +1125,26 @@ int sysctl_extfrag_threshold = 500;
* @nodemask: The allowed nodes to allocate from
* @mode: The migration mode for async, sync light, or sync migration
* @contended: Return value that is true if compaction was aborted due to lock contention
- * @page: Optionally capture a free page of the requested order during compaction
+ * @candidate_zone: Return the zone where we think allocation should succeed
*
* This is the main entry point for direct page compaction.
*/
unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask,
- enum migrate_mode mode, bool *contended)
+ enum migrate_mode mode, bool *contended,
+ struct zone **candidate_zone)
{
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
int may_enter_fs = gfp_mask & __GFP_FS;
int may_perform_io = gfp_mask & __GFP_IO;
struct zoneref *z;
struct zone *zone;
- int rc = COMPACT_SKIPPED;
+ int rc = COMPACT_DEFERRED;
int alloc_flags = 0;
/* Check if the GFP flags allow compaction */
if (!order || !may_enter_fs || !may_perform_io)
- return rc;
-
- count_compact_event(COMPACTSTALL);
+ return COMPACT_SKIPPED;
#ifdef CONFIG_CMA
if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
@@ -1156,14 +1155,33 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
nodemask) {
int status;
+ if (compaction_deferred(zone, order))
+ continue;
+
status = compact_zone_order(zone, order, gfp_mask, mode,
contended);
rc = max(status, rc);
/* If a normal allocation would succeed, stop compacting */
if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0,
- alloc_flags))
+ alloc_flags)) {
+ *candidate_zone = zone;
+ /*
+ * We think the allocation will succeed in this zone,
+ * but it is not certain, hence the false. The caller
+ * will repeat this with true if allocation indeed
+ * succeeds in this zone.
+ */
+ compaction_defer_reset(zone, order, false);
break;
+ } else if (mode != MIGRATE_ASYNC) {
+ /*
+ * We think that allocation won't succeed in this zone
+ * so we defer compaction there. If it ends up
+ * succeeding after all, it will be reset.
+ */
+ defer_compaction(zone, order);
+ }
}
return rc;
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